diff --git a/src/microdot/microdot.py b/src/microdot/microdot.py
index 4bfa005..3d84920 100644
--- a/src/microdot/microdot.py
+++ b/src/microdot/microdot.py
@@ -13,6 +13,7 @@ import time
 
 try:
     from inspect import iscoroutinefunction, iscoroutine
+    from functools import partial
 
     async def invoke_handler(handler, *args, **kwargs):
         """Invoke a handler and return the result.
@@ -23,7 +24,7 @@ try:
             ret = await handler(*args, **kwargs)
         else:
             ret = await asyncio.get_running_loop().run_in_executor(
-                None, handler, *args, **kwargs)
+                None, partial(handler, *args, **kwargs))
         return ret
 except ImportError:  # pragma: no cover
     def iscoroutine(coro):
diff --git a/tests/test_microdot.py b/tests/test_microdot.py
index f99d571..e0bf255 100644
--- a/tests/test_microdot.py
+++ b/tests/test_microdot.py
@@ -25,6 +25,14 @@ class TestMicrodot(unittest.TestCase):
         async def index2(req):
             return 'foo-async'
 
+        @app.route('/arg/<id>')
+        def index3(req, id):
+            return id
+
+        @app.route('/arg/async/<id>')
+        async def index4(req, id):
+            return f'async-{id}'
+
         client = TestClient(app)
 
         res = self._run(client.get('/'))
@@ -45,6 +53,24 @@ class TestMicrodot(unittest.TestCase):
         self.assertEqual(res.body, b'foo-async')
         self.assertEqual(res.json, None)
 
+        res = self._run(client.get('/arg/123'))
+        self.assertEqual(res.status_code, 200)
+        self.assertEqual(res.headers['Content-Type'],
+                         'text/plain; charset=UTF-8')
+        self.assertEqual(res.headers['Content-Length'], '3')
+        self.assertEqual(res.text, '123')
+        self.assertEqual(res.body, b'123')
+        self.assertEqual(res.json, None)
+
+        res = self._run(client.get('/arg/async/123'))
+        self.assertEqual(res.status_code, 200)
+        self.assertEqual(res.headers['Content-Type'],
+                         'text/plain; charset=UTF-8')
+        self.assertEqual(res.headers['Content-Length'], '9')
+        self.assertEqual(res.text, 'async-123')
+        self.assertEqual(res.body, b'async-123')
+        self.assertEqual(res.json, None)
+
     def test_post_request(self):
         app = Microdot()